Entering the final match of the 2018 World Cup, five of the 14 knockout stage games that have been played have gone into extra-time.

Croatia’s semi-final win over England was only their most recent to require 30 draining added minutes. The second smallest nation to ever reach the tournament’s final round played extra-time in each of their three knockout stage matches.

As the Croatian and English stars grinded through the added time, fatigue visibly took hold. Bones creaked and muscles ached. Passes missed their mark and dribbles slipped through the feet of the world’s most skilled players. Exhaustion can make even the most fundamental skills a challenge.

Indeed, as extra-time becomes more common, there is an increasing need to help players push through the fatigue. Sports science researchers at the University of Huddersfield are working to find ways to give soccer players that extra edge in extra-time.

Why fatigue takes a toll

Liam Harper, a senior lecturer in sport, exercise and nutrition sciences at the University of Huddersfield, noted that fatigue has a demonstrable impact on extra-time play.

He participated in two studies on the effects of exhaustion on extra-time performance in two articles, entitled “Technical Performance Reduces during the Extra-Time Period of Professional Soccer Match-Play” and “Are soccer players going the extra mile in extra-time?.”

Harper’s research shows that players are less likely to be involved in build-up play during extra-time and are less precise with passes and dribbles.

Harper also notes that small case studies have suggested that playing extra-time can affect recovery time and performance in subsequent matches, though more expansive studies are required to draw concrete conclusions.

“We have looked at a lot of the physiological responses to explain this and the main one is a change in energy substrate use,” Harper said in a statement. “Typically, towards the end of a 90-minute game you start to reduce the amount of muscle glycogen (stored carbohydrate). So it is likely this reduces further during extra-time. Muscle glycogen stores are the source that contributes most to high-intensity running and sprinting, which is crucial to successful performance in football.”

What can be done to gain extra edge?

Harper and his colleagues have searched for ways to help players cope with the physical demands of added time.

Their research has shown that the five-minute break before the beginning of extra-time is key.

There is also evidence that nutritional supplements, such as carbohydrate gels or caffeine gum, may provide an extra edge.

“Carbohydrate has been consistently shown to be beneficial for performance in a wide range of sports, including football,” said Harper. “However, the effectiveness of gels prior to extra-time hadn’t been assessed, although anecdotally and from a survey we did with practitioners, players do consume them prior to extra-time.”

In one study, young players in Sunderland Association Football Club’s academy were given 46 grams of carbohydrate in gel form during the five-minute break before extra-time and evaluated on their performance.

The researchers found that the players’ physical performance did not demonstrably improve, but their dribbling accuracy was bolstered by the supplements.

“This is likely reflective of the carbohydrate having an influence on the central nervous system through receptors in the mouth,” said Harper. “We did not provide the players carbohydrate during the warm-up and at half-time, which is normal practice in football, so this was a limitation of the study.”

There is some resistance within professional football to the idea of increasing nutritional supplements.

In a survey with 46 practitioners who work in the professional game, Harper and his colleagues found that most advocate nutrition before extra-time. However, he noted that many only support drinking water, not taking carbohydrates. Furthermore, taking carbohydrate supplements over the course of the game — at the half-time break, for example — is very uncommon.

Harper suggests that new nutritional ideas could be beneficial to the game, and has a few recommendations for teams looking to gain a leg up in extra-time.

He advocates “ensuring that carbohydrate is consumed throughout match-play, including the five-minute break before extra-time and in the two minute break between extra-time halves if possible.”

“Caffeinated products like gum may also be beneficial, providing the players have tried it during other matches in training so that they know they won’t react adversely to it. And of course, ensuring hydration is optimal,” he added.

As Harper continues his research on extra-time, he will work with a doctoral student to examine the recovery response following extra-time matches under more controlled conditions.

He also intends to further his research on nutritional interventions.